use_article()

[jennybc]

We need use_article() which is a minor variant on use_vignette().

What's wrong with using use_vignette() to create an article?

1. If you only have articles, you want to Rbuildignore the directory that contains them. So either vignettes/ or vignettes/articles/.
2. Creation of an article should never trigger an edit to DESCRIPTION. Specifically, do not add a VignetteBuilder field.
3. The article itself should not have a vignettes: section in the yaml header.

To see me recovering from all of the above mistakes, look at these travis ci reports:

https://travis-ci.org/r-lib/usethis/builds/344519915

https://travis-ci.org/r-lib/usethis/builds/345021574

https://travis-ci.org/r-lib/usethis/builds/345023872

[hadley]

1 feels a bit tricky to me (what if you want a mix of articles and vignettes) so I'm just going to do 2 and 3.

[hadley]

I'm pretty sure we should still add rmarkdown to Suggests, just to ensure that it's always installed on travis (it probably is because pkgdown imports it, but better to be explicit here, I think)

[hadley]

Oh I can just ignore articles by default.